Place chocolate wafers, sugar and melted butter in a food processor. Process until finely ground. Spray the bottom of a 9x13 pan with non-stick cooking spray. Lightly press the cookie crust into the bottom of the pan. In a large bowl with an electric mixer, whip the cream until stiff peaks form. Set aside. In another large bowl with an electric mixer, beat the cream cheese until fluffy. Beat in the sweetened condensed milk and the chocolate syrup. In a small bowl, combine the espresso powder and water, stir until blended. Add this to the cream cheese mixture and beat until everything has been incorporated. Fold the whipped cream into the cream cheese mixture. Pour this mixture over the crust and smooth the top with an offset spatula. You can garnish the top of the cheesecake with crushed toffee bars, espresso beans or chocolate designs. Cover with plastic wrap and freeze overnight.